双面共体反射镜结构优化设计与分析

Optimization design and analysis of double-sided integrated mirror structure

为了满足某同轴四反红外光学系统中主四双面共体反射镜的性能要求,需要镜体在高轻量化率的同时具有更高的刚度,保持两个镜面面形稳定。该文采用拓扑优化的方法,以刚度最大为优化目标,约束设计域体积分数的方式对双面共体反射镜初始模型进行优化。优化结果表明,主镜面与四镜面通过以光轴为中心呈辐射形排列的筋板连接时刚度较高;通过自由尺寸优化获得主、四镜面和筋板的最佳尺寸参数;参考优化结果设计主、四共体反射镜,最终方案轻量化率达到82.4%。对主四反射镜模态及1g重力对面形RMS的影响进行分析,求得一阶频率达到417 Hz;1g重力作用下反射镜面形变化最大为λ/22(λ=632.8 nm)。分析结果表明,优化后的镜体刚度足够,且具有较好的抵抗重力变形能力。按照优化后的设计方案进行反射镜的加工和测试,主、四镜面形RMS实测结果均约λ/7,满足红外光学系统的性能要求,证明了本文优化设计方法的有效性,为双面共体反射镜的设计提供一定的借鉴作用。

In order to meet the needs for the performance of the primary-fourth double-sided integrated mirror in a certain on-axis four-mirror infrared optical system,the mirror body needs to have higher stiffness with high lightweight rate to keep the two mirror face shapes stable.The topology optimization method was used to optimize the initial model of double-sided integrated mirror with the maximum stiffness was set as the optimization objective,and the volume fraction of the design domain was constrained.The optimization results show that the stiffness is higher while the primary mirror and the fourth mirror are connected through ribbed plate arranged radially around the optical axis.The optimal size parameters for the primary-fourth and ribbed plate were obtained by free size optimization.Based on the optimization results,the primary-fourth double-sided integrated mirror was designed,and the lightweight rate achieved 82.4%by using the final solution.The mode of the primary-fourth double-sided integrated mirror and the influence of 1 g gravity on the root-mean-square(RMS)of the surface shape were analyzed,a first-order mode frequency achieved 417 Hz,and the maximum change of surface shape under gravity was 1/22λ(λ=632.8 nm).The analysis results show that the optimized mirror body has sufficient stiffness and good resistance to the deformation under gravity.The mirror was processed and tested according to the final design,and the measured results show that the RMS of primary-fourth mirror surface shapes are both aboutλ/7,which meets the needs for the performance of infrared optical systems,proves the effectiveness of this topology optimization design method,and provides some references for the optimization design of double-sided integrated mirrors.